PHYSICAL DEVELOPMENT IN INFANCY

CHAPTER 4

Learning Objectives

GROWTH AND STABILITY

Physical Growth: The Rapid Advances of Infancy

Infants grow at a rapid pace over the first two years of their lives (see Figure 4-1)•5 months: average birth weight doubles to around 15 #

•1 year: weight triples to about 22 pounds

•End of 2nd year: average child weighs around four times as much as at birth

How they grow…

Continuous

Physical Growth: The Rapid Advances of Infancy

Not all parts of an infant's body grow at the same rate•At Birth:

head accounts for one-quarter of newborn's entire body

•During 1st & 2nd year:

rest of the body begins to catch up

An Interesting Head Count

There are gender and ethnic differences in infant weight and length

• Girls generally are slightly shorter than boys• Girls weigh slightly less than boys • Gender differences remain throughout childhood • Asian infants tend to be slightly smaller than

NA Caucasian infants• African-American infants tend to be slightly bigger than

NA Caucasian infants.

Physical Growth:The Rapid Advances of Infancy

4 Principles

Nervous System and Brain:A Foundation of Development

• Neurons are the basic cells of the nervous system

• Nervous system comprises the brain and the nerves that extend throughout the body

Brain Development

Prenatal•Neurons multiply at an amazing rate prior to birth. •At some points in prenatal development, cell division creates some 250,000 additional neurons every minute.

Birth•100-200 billion neurons•Relatively few neurons-neuron connections

During first two years•Billions of new connections established and become more complex

Adult•A single neuron is likely to have a minimum of 5,000 connections to other neurons or other body parts.

Use it or lose it!

Although synapses are formed throughout life, based on our changing experiences, the billions of new synapses infants form during the first two years are more numerous than necessary

•Synaptic pruning– Unused neurons are eliminated– Allows established neurons to build more elaborate

communication networks with other neurons– Development of nervous system proceeds most effectively

through loss of cells

•Myelination• “Insulation” of the wiring• Protects & speeds information conduction• Activity-dependent effects on myelination cannot be

considered strictly a developmental event. (Fields, D.,Myelination: An Overlooked Mechanism of Synaptic Plasticity? Neuroscientist 2005)

Babies are born with many more neurons than they need

Neuron Networks

Over the first two years of life, networks of neurons become increasingly complex and interconnected.

Coming to terms with your brain…

Form and Function: Brain Growth

Neurons reposition themselves with growth, becoming arranged by function •Cerebral cortex

– upper layer of the brain– higher-order processes: thinking & reasoning– become more developed and interconnected

•Subcortical levels– Lower layers of the brain– regulate fundamental activities: breathing & heart rate– most fully developed at birth.

Brain Development: Influences and Definitions

the degree to which a developing structure or behavior is modifiable due to experience

a specific, but limited, time, usually early in an organism's life, during which the organism is particularly susceptible to environmental influences relating to some particular facet of development

What do babies do all day?

Integrating the bodily systems: Life cycles of infancy•Rhythms: repetitive, cyclical patterns of behavior

– Wake– Sleep– Eat– Eliminate

Initially like separate individuals all playing their own melody.Eventually they become like a jazz band still playing their own riff but weaving a single, harmonious, song.

Rhythms and States

State•One of major body rhythms•Degree of awareness infant displays to both internal and external stimulation•Change in state alters amount of stimulation required to get infant's attention•Electrical brain waves can be measured by electrocephalogram (EEG)

Primary Behavioral States

Primary Behavioral States

Sleep: Perchance to Dream

Major state•16-17 hours daily (average); wide variations•heart rates increase and become irregular, their blood pressure rises, and they begin to breathe more rapidly

Different than adult sleep•2 hour spurts; periods of wakefulness•Cyclic pattern•By 16 weeks sleep about 6 continuous hours; by 1 year sleep through night

Cycle of Infant Behavioral States

REM Sleep

• Period of active sleep

• Closed eyes begin to move in a back-and-forth pattern

• Takes up around one-half of infant sleep

• May provide means for brain to stimulate itself through autostimulation

• In Adults correlated with memory storage Why not in babies too?

REM Sleep Through the Lifespan

Did you find examples in the text that suggest that cultural practices affect infants’ sleep

patterns?

• the Kipsigis of Africa, infants sleep with their mothers and are nurse whenever they wake.

• They accompany their mothers during daily chores, napping while strapped to their mothers’ backs

• Kipsigis infants do not sleep through the night until much later than babies in Western societies,

• the first 8 months of life, they seldom sleep longer than 3 hours at a stretch.

• In comparison, 8-month-old infants in the United States may sleep as long as 8 hours at a time

Muc

h lik

e U

S b

reas

t fe

d ki

ds

SIDS: The Unanticipated Killer

• Sudden infant death syndrome (SIDS) is a disorder in which seemingly healthy infants die in their sleep

• SIDS strikes about 2,500 infants in the United States each year

• Although it seems to occur when the normal patterns of breathing during sleep are interrupted, scientists have been unable to discover why that might happen

SIDS

• Don’t shut the nursery door!• Use your EARS!

Declining Rates of SIDS

SIDS is found in children of every race and socioeconomic group and in children who have

had no apparent health problems

• SIDS strikes about 1 in 1,000 infants in the USA each year. • Although it seems to occur when the normal patterns of

breathing during sleep are interrupted, scientists have been unable to discover why that might happen.

• American Academy of Pediatrics now suggests that – babies sleep on their backs rather than on their sides or

stomachs—called the back-to-sleep guideline. – parents consider giving their babies a pacifier during naps

and bedtime.

Back-to-sleep is important!

MOTOR DEVELOPMENT

Motor Development

• Shape and proportions of newborn babies are simply not conducive to easy mobility

• Young infants lack the strength to raise large heads

• Movement is further impeded because limbs are short in relation to the rest of the body

• Infant bodies are mainly fat, with a limited amount of muscle; the result is a lack strength

Motor Development

BUT•At birth newborns have an extensive repertoire of behavioral possibilities brought about by innate reflexes, and their range of motor skills grows rapidly during the first two years of life

Reflexes: Inborn Physical Skills

Reflexes•Learned, organized involuntary responses that occur automatically in presence of certain stimuli

WHAT?

No, No! Reflexes are wired up unlearned responses to stimuli!

Some Basic Reflexes in Infants

Some Basic Reflexes in Infants

Why do neonate reflexes come and go?

1. Evolutionary explanations of development: gradual disappearance of reflexes to result of increase in voluntary control over behavior that occurs as infants become more able to control their muscles.

2. It may be that reflexes form the foundation for future, more complex behaviors. As these more intricate behaviors become well learned, they encompass the earlier reflexes.

3. Perhaps reflexes stimulate parts of the brain responsible for more complex behaviors, helping them develop.

Intensive practice of motor behaviors

• May produce earlier appearance of certain motor activities

• No evidence the activities are performed qualitatively better

• Even when early gains are found• Do not produce a child w/ better motor skills• Do not produce an adult w/ better motor skills.

Ethnic and Cultural Differences and Similarities in Neonatal Reflexes

Reflexes•Genetically determined•Universal

Cultural variations in ways displayed•Moro reflex

Serves•Diagnostic tool

• reflexes emerge and disappear on a regular timetable

• their absence—or presence—at a given point of infancy

• a clue that something’s wrong in an infant's development.

•Social function•Survival function

Moro Reflex: Some differences reflect cultural and ethnic variations

• Caucasian infants show a pronounced response.– Also cry and respond in a generally agitated manner.–

• Navajo babies react much more calmly. – Arms do not flail out as much and rarely cry.

Moro Reflex (Startle Reflex) - stretch out the arms, flex the legs, and grab.

Milestones of Motor Development

• Fifty percent can perform each skill at the month indicated in the figure.

• Timing at which each skill appears varies widely.• 24% walk well at 11.1 months• 90% by 14.9 months

Motor Progress

• Young infants still are able to accomplish some kinds of movement.• When placed on their stomachs they wiggle their arms and legs and may try

to lift their heavy heads. • As their strength increases, they are able to push hard enough against the

surface on which they are resting to propel their bodies in different directions.

• They often end up moving backwards rather than forwards, but by the age of 6 months they become rather accomplished at moving themselves in particular directions.

• These initial efforts are the forerunners of crawling, in which babies coordinate the motions of their arms and legs and propel themselves forward.

• Crawling appears typically between 8 and 10 months.• Walking comes around the age of 9 months; most infants are able to walk

by supporting themselves on furniture, and half of all infants can walk well by the end of their first year of life.

• Most are able to sit without support by the age of 6 months.

Dynamic Systems

Dynamic systems theory •Describes how motor behaviors are assembled

– Motor skills do not develop in vacuum– Each skill advances in context of other motor abilities– As motor skills develop, so do non-motoric skills

•Theory places emphasis on child's own motivation (a cognitive state) in advancing important aspects of motor development

Developmental Norms

Comparing Individual to Group Norms:•Represent the average performance of a large sample of children of a given age•Permit comparisons between a particular child's performance on a particular behavior and the average performance of the children in the norm sample•Must be interpreted with caution

•Brazelton Neonatal Behavior Assessment Scale (NBAS)

Nutrition in Infancy

Fueling Motor Development•Without proper nutrition, infants cannot reach physical potential and may suffer cognitive and social consequences

•Infants differ in growth rates, body composition, metabolism, and activity levels

So what is a healthy caloric allotment for infants?

• About 50 calories per day for each pound of weight

• Most infants regulate their caloric intake quite effectively on their own

• If are allowed consume as much they seem to want, and not pressured to eat more, they will be healthy

Malnutrition

Malnutrition•Condition of having improper amount and balance of nutrients, produces several results, none good

•More common in children living in developing countries

•Slower growth rate

•Chronically malnourished during infancy• later lower IQ score• Do less well in school• Effects linger even after improved diet

Underweight Children

Percent under five years who are moderately or severely underweight.

Are problems of malnourishment restricted to developing countries?

Undernutrition: Dietary Deficiencies

• Undernutrition also has long-term costs, including mild to moderate cognitive delays

• Up to 25% of 1- to 5-year-old US children have diets that fall below minimum caloric intake recommended by nutritional experts

• 1/5 of US children go to bed hungry.

• Do you believe these “statistics”?

When Malnutrition Is Severe

Maramus•Malnutrition in first year•Infants stop growing.•Attributable to severe deficiency in proteins and calories•Causes the body to waste away •Ultimately results in death

Kwashiorkor•Found in older children•Child's stomach, limbs, and face swell•Body struggles to make use of few available nutrients

Nonorganic Failure to Thrive

• Sufficient nutrition• but are deprived of attention and stimulation.

• Symptoms • underdevelopment, listlessness, and apathy • usually occurs by age 18 months.

• Reversal• possible through intensive parent training • or removal to emotionally supportive environment.

“A fat baby is a healthy baby.” Really?

• Not necessarily.

• No clear correlation between obesity during infancy and obesity at 16 years

• BUT - some research suggests overfeeding during infancy may lead to the creation of an excess of fat cells

• remain in the body throughout life • may predispose a person to be overweight.

• Weight gain during infancy may relate to weight at 6• Weight at 6 associated with adult obesity.

Is Breast Best?

Starting around the 1940s, the general belief among “child care experts” was that breast-feeding was an obsolete method that put children unnecessarily at risk.

Bottle-feeding argument: •keep track of amount of milk baby was receiving •could ensure that child got sufficient nutrients. •helped mothers keep feedings to rigid schedule of one bottle every 4 hours (the recommended at that time)•Mothers who breast-fed their babies could never be certain just how much milk their infants were getting.

Is Breast Best?

Breast-feeding argument: •First 12 mos no better food for an infant than breast milk.•Contains all the nutrients necessary for growth •Offer some immunity to a variety of childhood diseases

• respiratory illnesses• ear infections• diarrhea• allergies.

•More easily digested than cow's milk or formula•It’s sterile, warm, and convenient for mother to dispense. •Breast milk may enhance cognitive growth

• Leads to high adult intelligence.• Babies are more responsive to touch.

Is Breast Best?

For mother: •lower rates of ovarian cancer and breast cancer prior to menopause. •Hormones produced during breast-feeding help shrink uteruses of women following birth•enables mom’s bodies to return more quickly to a pre-pregnancy state. •Hormones also may inhibit ovulation,

• reducing (but not eliminating!) chance of becoming pregnant

• thereby helping to space birth of additional children

So What Is the Answer?

Breast milk•Offers all nutrients infant needs for first 12 months of life•Is more easily digested than alternative•Provides some immunity to variety of childhood diseases•May enhance cognitive growth•Offers significant emotional advances for mother and child•Not cure-all for infant nutrition and health

Introducing Solid Foods: When and What?

• Solids can be started at 6 months but are not needed until 9 to 12 months (AAFP)– Introduced gradually, one at a time– Cerealstrained fruits

• Time of weaning varies greatly in developed and developing countries

Learning the World

• Sensation

is the physical stimulation of the sense organs

• Perception

is the mental process of sorting out, interpreting, analyzing, and integrating stimuli from the sense organs and brain

Visual Perception: Seeing the World

• Newborn's distance vision ranges from 20/200 to 20/600 distance vision is 1/10th to 1/3rd that of average adult's.

• By 6 months, average infant's vision is already 20/20

• Other visual abilities grow rapidly– Binocular vision– Depth perception

Infant Visual Preference

Preferences that are present from birth•Genetically preprogrammed to prefer particular kinds of stimuli

•Prefer to look at patterned over simpler stimuli•Robert Fantztwo- and three-month-old infants

Neonate Visual Preferences

• Prefer – curved over straight lines– three-dimensional figures to two-dimensional ones, – human faces to non-faces.

Such capabilities may be a reflection of the existence of highly specialized cells in the brain that react to stimuli of a particular pattern, orientation, shape, and direction of movement.

• Prefer their own mother's face to other faces; • Distinguish between male and female faces

Facing the World

Genetics is not the sole determinant of infant visual preferences

•A few hours after birth, infants have already learned to prefer their own mother's face to other faces

•Similarly, between the ages of six and nine months, infants become more adept at distinguishing

•between the faces of humans, while they become less able to distinguish faces of members of other species

•They also distinguish between male and female faces

Auditory Perception: The World of Sound

Infants •Hear before birth and have good auditory perception after birth

•Are more sensitive to certain frequencies

•Reach adult accuracy in sound localization by age 1

•Can discriminate groups of different sounds

•React to changes in musical key and rhythm

•Can discriminate many language related sounds

•Are born with preferences for particular sound combinations which may be shaped by prenatal exposure to mothers’ voices

Smell and Taste in a Small World

Smell•Well developed at birth•Helps in recognition of mother early in life•Used to distinguish mother's scent (only in breast fed babies); cannot distinguish father on basis of odor

Taste•Have innate sweet tooth•Show facial disgust at bitter taste•Preferences based on what mother ate during pregnancy

Ouch!

Contemporary Views on Infant Pain

•Today, it is widely acknowledged that infants are born with the capacity to experience pain

•Developmental progression in reaction to pain

•Infants born with capacity to experience pain; produces distress

•Exposure to pain in infancy may lead to permanent rewiring of nervous system resulting in greater sensitivity to pain during adulthood

The Power of Touch

• Touch is one of most highly developed sensory systems in a newborn

• Even youngest infants respond to gentle touches

• Several of the basic reflexes present at birth require touch sensitivity to operate

Multimodal Perception: Combining Individual Sensory Inputs

New area of study in infant research•Some researchers argue that sensations are initially integrated with one another in the infant

•Others maintain that infant's sensory systems are initially separate and that brain development leads to increasing integration

•It does appear that by an early age infants are able to relate what they have learned about an object through one sensory channel to what they have learned about it through another

What are affordances?

Perceptible affordances •Exist where information on actions that are afforded are perceptible

•These are dependent on language, culture, context, and experience and vary for different individuals

Becoming an Informed Consumer of Development

• Exercising Your Infant's Body and Senses

Attempts to accelerate physical and sensory-perceptual development yield little success

butinfants need sufficient physical and sensory stimulation.

Enrichment

• Carry a baby in different ways

• Let infants explore their environment

• Engage in “rough-and-tumble” play

• Let babies touch their food and even play with it

• Provide toys that stimulate the senses, particularly toys that can stimulate more than one sense at a time

• Expose them to varied social environments

Be Normal!